1. Field of the Invention
The present invention relates to a water-soluble isoflavone composition, its preparation and use, more particularly, to a water-soluble isoflavone composition which has an improved water-solubility, immediate activity during absorption, and sustainable physiological activity after absorption; and its preparation and use.
2. Description of the Related Art
Isoflavone and derivatives thereof (isoflavone derivatives) have been known to have an effect of preventing an excessive exudation of calcium from the bone so as not to lose supplemented calcium, and also known to prevent osteoporosis often found in elderly persons, attenuate the unbalance of female sex hormones, prevent climacteric disturbance by supplementing substances capable of functioning as a female sex hormone, inhibit the oxidation of cholesterol, prevent arteriosclerosis, and to prevent geriatric diseases such as hyperlipemia. Therefore, it has been recommended to take soybean isoflavone and derivatives thereof and various methods for extracting such compounds have been proposed.
Examples of therapeutic methods for treating the aforesaid osteoporosis with medicaments include conventional administrations of calcium agents, active vitamin D3 agents, and female sex hormone agents. The onset of osteoporosis would be effectively prevented by improving daily life-style habits including meals and exercises so as not to lower the bone density. Particularly, the secretion level of estrogen, as a female sex hormone, in postmenopausal females will be lowered, resulting in an increment of risks of the onset of climacteric disturbances such as arteriosclerosis, hyperlipemia, and hypertension, as well as postmenopausal osteoporosis. Accordingly, positive intake of soybean isoflavones and derivatives thereof would be desirable as a means for preventing such diseases.
If isoflavone derivatives or compositions thereof, which are promptly absorbed by the body and kept therein at a relatively high concentration for a longer period of time, are explored, they would have a great significance.
However, there have not yet been proposed any foods or pharmaceuticals containing such a nutrient or pharmaceutical component which can be promptly absorbed by the body and then kept therein for a longer period of time and which is capable of more positively preventing the onset of osteoporosis, arteriosclerosis, and climacteric disturbances.
Therefore, if the exudation of calcium could possibly be reduced or even prevented by daily intake of foods, health foods, etc., while maintaining the bone density, preventing the onset of osteoporosis, or treating osteoporosis, then it must be highly useful. Thus, there has been desired the establishment of such a novel health food or pharmaceutical, which can easily and safely increase the bone density and prevent osteoporosis.
Similarly as above, there has been also desired the establishment of such a novel health food, pharmaceutical or cosmetic, which can attenuate the unbalance of female sex hormones, prevent climacteric disturbance by supplementing substances functioning as a female sex hormone, inhibit the oxidation of cholesterol, prevent arteriosclerosis, and prevent geriatric diseases such as hyperlipemia.
The present inventors further energetically studied on conventionally proposed methods for extracting derivatives of soybean isoflavone, methods for improving their water solubility, and products obtainable therewith.
Examples of the above methods for extracting derivatives of soybean isoflavone and for improving their water solubility are as follows:
A method comprising the steps of contacting a soybean extract with a synthetic adsorption resin to adsorb isoflavone thereupon, and eluting the adsorbed isoflavone from the resin with an organic solvent or a mixture of water and an organic solvent (Japanese Patent Laid-Open Publication No. 126,186/87);
A method for producing an isoflavone compound, comprising the steps of extracting soybean germ with a water-soluble organic solvent, concentrating the extract, and removing lipophilic components from the concentrate, followed by reconcentrating, purifying, and drying the resultant (Japanese Patent Laid-Open Publication No. 263,786/99);
A method for producing an extract of water-soluble isoflavone derivative, comprising the steps of dissolving by heating an extract of isoflavone derivative derived from soybean in ethanol solution in the presence of a branched-type maltosyl α-cyclodextrin, and removing insoluble substances from the resulting mixture after cooling (Japanese Patent Laid-Open Publication No. 2002-155,072); and
A method for producing a readily water-soluble soybean isoflavone, comprising the steps of mixing a crude extract obtained from a soybean material, and removing insoluble materials from the resulting mixture after mixing with cyclodextrin in an aqueous solution (Japanese Patent Laid-Open Publication No. 298,175/98).
In addition, there has been proposed inclusion products, prepared by allowing β- or γ-cyclodextrin to include isoflavone derivatives, which have a suppressed bitterness, etc., a relatively high water solubility, and a relatively high absorption efficiency by the body (Japanese Patent Laid-Open Publication No. 309,902/97).
However, for example, the extracts obtained by the methods in Japanese Patent Laid-Open Publication Nos. 126,186/87 and 263,786/99 have a poor water-solubility as disclosed in Japanese Patent Laid-Open Publication No. 2002-155,072. Similarly, the inclusion product disclosed in Japanese Patent Laid-Open Publication No. 309,902/97 has a moot point of improving its solubility and stability in aqueous solutions.
Although the above-identified Japanese Patent Laid-Open Publication No. 2002-155,072 discloses that the method disclosed therein effectively yields an extract of isoflavone derivative, there's a moot point of improvement in terms of the yield of isoflavone and derivatives thereof due to the fact that even ethanol-soluble impurities, contained in a crude soybean extract, are exuded into a filtrate and then collected. When used after α-glucosylation in the presence of a saccharide and a saccharide-transferring enzyme, the obtained inclusion product of isoflavone or derivatives thereof should be subjected to volatilization/removal of ethanol prior to the above enzymatic modification, because ethanol contained in the inclusion product inhibits the activity of such an enzyme. As disclosed in the above-identified Japanese Patent Laid-Open Publication No. 2002-155,072, the method disclosed in Japanese Patent Laid-Open Publication No. 298,175/98 could only produce a readily water-soluble soybean isoflavone in a yield of about 10% and there's a moot point of further improvement in terms of the yield of isoflavone and derivatives thereof.
Japanese Patent Laid-Open Publication No. 2000-327,691 discloses a method for producing isoflavone derivatives derived from soybean or aglycone thereof, which comprises the steps of extracting isoflavone derivatives from soybean and/or a processed soybean product with any one of an alkaline solution with a pH of 8 or higher, hot water, or an organic solvent; allowing an α-glycosyl saccharide compound and a saccharide-transferring enzyme to act on the resulting extract to form α-glycosyl isoflavone derivatives; and removing impurities as precipitates from the resulting mixture by either adjusting the pH of the mixture to an acid pH of 5.5 or lower, or cooling the mixture.
In the method disclosed in Japanese Patent Laid-Open Publication No. 2000-327,691, the produced α-glucosyl isoflavone derivatives derived from soybean need improvement because they are relatively high in color valency and susceptible to decomposition reaction, due to the fact that they contain impurities originating from soybean other than isoflavone and derivatives thereof and have been prepared by enzymatic reaction under an alkaline condition.    Patent Document 1: Japanese Patent Laid-Open Publication No. 126,186/87    Patent Document 2: Japanese Patent Laid-Open Publication No. 263,786/99    Patent Document 3: Japanese Patent Laid-Open Publication No. 2002-155,072    Patent Document 4: Japanese Patent Laid-Open Publication No. 298,175/98    Patent Document 5: Japanese Patent Laid-Open Publication No. 309,902/97    Patent Document 6: Japanese Patent Laid-Open Publication No. 2000-327,691